Audition from the lowest price to the out of this world price. Compare the reaction of your brain and ears to the sound that you hear. Bring your own CD or LP, and source player - cd player or turntable.
Again, dont let price be the deciding factor. When you get to know which brands are good for you, then that would be the time for you to decide and weigh in the factors.
Also, get to know more about tube types - 6550, el34, kt88, 6l6gc, 2a3, 300B, el84. Mahihilo ka sa dami, sa totoo lang.